I am adding a bathroom on the second floor of my home. The question I have is: is there a maximum distance that my horizontal waste line can be from my main waste line, I have proper venting on the second floor through the roof. The problem is the bathroom is on the opposite side of the house from the existing 4" main. I have a strait shot vertically to the basement from the bathroom. The branch wasteline will have to run across about 20 feet of basement to reach the main waste line out to the septic tank. Am I ok as long as the 3" branch is sloped to the 4" main (1/4" per foot)?

No maximum length as long as you maintain the proper slope, 1/4" per foot for 3" and smaller pipes, half that for 4" and larger pipe.

Hi all:

As Ballengerb1 stated, you should be fine on the distance. Only concerns I have are that you may want to install a DANDY CLEAN OUT at the base of the stack and an END CLEAN OUT at any major changes of direction to the drain line... see images below.

You may also want to install another DANDY CLEAN OUT just before connecting into the main drain line.

These cleanouts come in awfully handy if drain line gets clogged or someone drops something down the drain in the future... ;)

Otherwise, you should be all set!

MARK